Looseleaf notebooks having two, three or even more rings which may be selectively opened or closed to accept pages having punched holes therein are well known to the art. The present invention is directed to an improvement in binders for looseleaf notebooks in which the binding mechanism is not a ring but a split cylinder having "clam-shell" type of construction. The loose-leaf pages of the new notebook will not have circular holes for mounting on rings, rather they will have one or more elongated slots for being removably mounted on the elongated cylindrical clam-shell holders. Significantly, small notebooks need have only one cylindrical leaf holder in the center of the spine for the new notebook to mount the pages thereof. This presents an extraordinarily attractive and simple construction.